The present invention relates to a fast spot gluing machine for screws, which is able to entirely spot glue the screws at increased speed.
FIGS. 1 and 2 show a conventional spot gluing machine for screws, having a vibrating body 10, a rectangular guide tube 20, a U-shaped fixing support 30, first and second gears 41, 42 opposite to each other, a stepped motor 50, a control circuit 60 and a glue compressing device 70. A spiral slope 11 is formed on an inner wall of the vibrating body 10, extending to a top thereof to connect with the guide tube 20. The guide tube 20 extends downward to a lower end and is formed with a lengthwise channel 21. The U-shaped support 30 fixedly retains the lower end of the guide tube 20 between the two gears 41, 42 and has two parallel arms 31, 32 formed with slots 311, 321 respectively. A glue injecting nozzle 71 is disposed above the second gear 42, whereby the glue compressing device 70 can compress and feed the glue to the nozzle 71 so as to be sprayed into the clearances between the teeth of the gear 42. The control circuit 60 is disposed behind the gears 41, 42 for controlling the stepped motor 50 to intermittently rotate the gears 41, 42.
Please refer to FIG. 3 which shows the operation of the conventional machine according to FIGS. 1 and 2. The screws to be glued are first placed into the vibrating body 10 which vibrates to make the screws move upward along the spiral slope 11 into the guide tube 20. The stem portion of each screw protrudes outside the guide tube 20 through the channel 21 thereof, while the head portion of the screw is restrained by the edge of channel 21 to move downward along the guide tube 20. The glue compressing device 70 operates synchronously with the stepped motor 50, whereby when the gears 41, 42 stop rotating, the glue compressing device 70 sprays the glue into the clearances between the teeth thereof. The screw sliding downward along the guide tube 20 will reach a position between the gears 41, 42 in a horizontal state and automatically drop into the clearance sprayed with the glue to be spot glued. When the two gears 41, 42 perform the next rotation, the spot glued screw automatically drops onto a conveying belt 80 disposed under the gears 41, 42. The same procedure is repeated continuously.
According to the above arrangements, three shortcomings exist as follows:
1. The screw is spot glued in cooperation with the intermittent rotation of the gears 41, 42 so that the spot gluing operation is performed at a low rate.
2. The two gears 41, 42 are fixedly disposed and unadjustably used only for screws having dimensions within a specific range.
3. The spot gluing cannot be applied to the entire surface of the stem portion of the screw and is applied only to a very small area of the stem portion of the screw, which is at most about 45 degrees of the surface of the stem portion. Therefore, the screw going through such spot gluing has relatively poor quality.
It is therefore necessary to provide an improved spot gluing machine for screws, which is able to continuously entirely spot glue different screws with various dimensions around 360 degrees of the surface and at increased speed.